1. Field of the Invention
The present invention relates to a solar type heat exchanger for converting incoming liquid to hot vapor.
2. Description of the Prior Art
In conventional prior art solar heat exchangers, a feed liquid entering the exchanger is normally either heated by sunlight energy to produce a non-boiling liquid at higher temperature or a percentage of the entering liquid is vaporized and the remainder accumulates and passes from the exchanger as a liquid. In the first type of solar heat exchanger commonly referred to as an indirect solar exchanger, the non-boiling liquid must be passed to a second (non-solar) conventional heat exchanger in which heat energy is transferred indirectly from the hot non-boiling liquid to another liquid such as water to vaporize the second liquid, so as to produce steam or other useful vapor. The disadvantage of this particular conventional type of system is that additional (non-solar) type indirect heat exchangers are required, thus adding to the cost and complexity of the sytem. On the other hand solar heat exchangers of the second type commonly referred to as insitu type exchangers disclosed in the prior art normally have a disadvantage of bulky design and lower heat transfer rate per unit tube surface area generally attributable to the greatly enlarged steam chamber required to accommodate the boiling liquid and steam produced within the exchanger. Another disadvantage of this latter type of solar heat exchanger is that in view of the reduced heat transfer rate only a portion of the incoming liquid is converted to vapor within the exchanger. The unconverted portion accumulates to form a liquid pool within the exchanger and excess liquid must be removed.
The present invention overcomes these disadvantages of the prior art solar heat exchangers by providing compact means for increasing the rate of heat transfer to the liquid passed into the exchanger so that virtually all incoming liquid is converted to steam or useful vapor within the solar exchanger itself without need for additional (non-solar) heat exchangers.